The invention relates to cable gland assemblies.
Cable gland assemblies typically provide a seal and a mechanical and/or electrical connection between a cable and a wall through which the cable passes. On oil production platforms, for example, cable glands may be used to prevent ingress of water into a junction box.
The applicants EP-A-0587310 discloses a cable gland assembly consisting essentially of an adaptor, a sleeve, a cap nut and a clamping arrangement. The adaptor and the sleeve are screwed together with the clamping arrangement effectively held captive therebetween, and the adaptor is screwed into a hole in a wall through which the cable is intended to pass. A seal seated in an annular recess within the cap nut is compressed axially when the cap nut is screwed onto the sleeve and the resulting radial deformation brings the seal into sealing engagement with the sheathing of a cable.
U.S. Pat. No. 6,162,995 describes a cable gland assembly which has a segmented clamping ring having two sets of pivotable fingers extending in opposite directions from a central portion which has a groove for receiving an xe2x80x9cOxe2x80x9d ring seal. One set of fingers are adapted to grip an armouring sheath on the cable within the gland assembly whilst the second set of fingers are adapted to close a plain tubular sealing sleeve down upon an outer sheath of the cable to seal therearound. However, once the second set of fingers have closed down to a predetermined aperture size it is not possible for them to close any further as they are all effectively locked together in a solid ring as the gaps between the fingers are defined by radially extending faces which are unable to slide relative to each other. A further disadvantage is that the only sealing of the interior of the gland assembly against ingress of fluids, other than the sealing sleeve, is the xe2x80x9cOxe2x80x9d ring seal which under some pressure conditions can be inadequate for the purpose.
In order to minimise the number of different component parts that need to be manufactured, stocked and supplied, there is a drive towards the universal cable gland, that is, a gland that can cope with a wide variety of types and sizes of cables. For example, the cap nut sealing mechanism described above is adapted, by virtue of radial deformation, to operate with a range of diameters of cable. However, in order to satisfy the full range, it is still necessary to manufacture several different seal sizes. If the range over which the seal operated could be improved still further, component manufacture could be additionally simplified.
Electrical cables are made up according to purpose, operating conditions etc. Generally, all cables have one or more central conducting cores, within insulating material, surrounded by sheathing. The type of sheathing may vary according to requirements and there may be one or more layers of sheathing: for instance, one of the layers may be of solid metal or wound or interwoven wires for mechanical protection or electrical screening. For example, cables intended for laying in underground cable channels may be sheathed with solid lead so as to prevent rats or other rodents biting through them.
For metal sheathed cables, there is a need to maintain electrical continuity between the metal sheathing and earth. Such continuity may be provided through the cable gland assembly, which may be earthed, for example, through a tag typically comprising an apertured plate clamped between parts of the assembly. In order to ensure an electrical connection between the sheathing and the assembly, an earth continuity device may be provided which bridges any electrical contact gap. For instance, for anti-rodent lead sheathing, a lead collar may be fitted around the exposed sheath and the assembly may be adapted to receive the collar such that, on screwing together the parts of the assembly, the collar is compressed into electrical contact with both the sheathing and the one or more of the parts.
According to a first aspect, the invention provides a cable gland assembly for sealing between a cable and a wall through which the cable passes, the assembly having a sealing mechanism comprising a sealing sleeve and a sealing sleeve urging device which on relative movement of two assembly parts is forced to urge the sealing sleeve in a sealing direction, the sealing sleeve urging device having a plurality of fingers mounted in a cylindrical formation on a support ring and wherein each finger is pivotable generally about the location at which the finger is mounted on the ring and each finger is relatively stiff thereby to remain substantially straight when forced to pivot, the assembly being characterised in that the sealing sleeve has a flange at one end of said sleeve.
The pivoting of the fingers brings about a displacement of the seal means and stiffness in the fingers facilitates the achievement of maximum degree of displacement. Hence, this contributes towards the achievement of a universal assembly. For example, in the event that the seal means and device are seated within the cap nut, the stiffness means that effective sealing can still be achieved even though the fingers of the device may be protruding out, beyond the open end of the cap nut.
The seal means may comprise a sealing sleeve. The sleeve may be top hat shaped, with a flange at one end. The outer surface of the sleeve may be profiled so as to include a recess. Each of the fingers may be provided with a projection which, on fitting the urging device and the sleeve together, extends into the sleeve recess. The projection and recess may prevent the sleeve from rucking or becoming misshapen so as to seal ineffectively. The flange may be scalloped such that, when the sleeve is fitted together with the urging device, the flange effectively wraps around the support ring of the urging device. The leading edge of the sleeve, that is the end opposite the flange, may be bull nosed or rounded. Both of the latter two features also assist in the sealing process. On relative movement of two parts of the assembly, the internal section of one of the parts may slide across the outer surface of the fingers, which section is shaped thereby to force the fingers in a sealing direction. The leading edge of the fingers may be tapered and the section of the part may be ramped so as to assist in the sliding process. The part may be the cap nut which is screwed on to the assembly at the end opposite to the end which passes through the wall.
According to a second aspect, the invention provides a cable gland assembly for sealing between a metal sheathed cable and a wall through which the cable passes having conducting means for bridging any electrical contact gap between the cable sheathing and a part of the assembly, which means comprises at least one resiliently flexible conductor.
A resiliently flexible conductor has the advantage over the prior art that it is not dedicated to one or, at least, a limited range of cable sizes, so it assists in the provision of a universal assembly. Also, it is not permanently deformed thereby enabling a cable to be removed, without damage, and re-used.